import collections
class Solution(object):
    def commonChars(self, words):
        """
        :type words: List[str]
        :rtype: List[str]
        """
        t = [collections.Counter(word) for word in words]
        key = t[0].keys()
        c = {k: min(dt[k] for dt in t) for k in key}
        out = []
        for k in c:
            out.extend([k] * c[k])
        return out